The psychedelic drug psilocybin has been found to cause long-term growth in neurons lost in depression.
The substance, a naturally occurring compound found in some mushrooms, has been studied as a potential treatment for depression for many years but scientists have not known why it appears to benefit those suffering from poor mental health.
In a new study, researchers from Yale University found that a single dose of psilocybin given to mice prompted an immediate and long-lasting increase in connections between neurons, helping repair the reduction in these caused by chronic stress and depression.
"We not only saw a 10 per cent increase in the number of neuronal connections, but also they were on average about 10 per cent larger, so the connections were stronger as well," said Yale's Alex Kwan, associate professor of psychiatry and of neuroscience and senior author of the paper.
Previous laboratory experiments had shown promise that psilocybin, as well as ketamine, can decrease depression.
The new Yale research, published in the journal Neuron, found that these compounds increase the density of dendritic spines, small protrusions found on nerve cells which aid in the transmission of information between neurons.
Using a laser-scanning microscope, Kwan and his colleague Ling-Xiao Shao, a postdoctoral associate in the Yale School of Medicine, found increases in the number of dendritic spines and in their size within 24 hours of administration of psilocybin.
Remarkably, these changes were still present a month later and mice exposed to stressful situations also showed behavioural improvements.
"It was a real surprise to see such enduring changes from just one dose of psilocybin," Kwan said. "These new connections may be the structural changes the brain uses to store new experiences."